1. Field of the Invention
The invention relates to a peripheral pump having a driven rotor, which rotates in a pump casing and in which a ring of blades is formed in each of its end sides for the purpose of delivering a liquid from an inlet duct to an outlet duct, and having annular ducts, which are formed in the pump casing on both sides in the region of the blades and, together with blade chambers between the blades, form delivery chambers which face one another, the rotor, in its radially inner region and in the region of its circumferential edge, facing toward the pump casing at a slight distance therefrom so as to delimit a sealing gap, and the blades, as seen in the direction of rotation, rising from the central region of the rotor toward the end sides.
2. Background of the Invention
Such peripheral pumps are often used to deliver fuel in a fuel tank of a motor vehicle and are therefore known. In this case, the delivery chambers are separated from one another by a central web arranged in the center of the rotor. When the rotor rotates, the blades generate in the delivery chambers a circulating flow which runs transversely to the direction of movement of the blades. On both sides of the rotor, this circulating flow runs from inlet ducts which are arranged on each side in the pump casing to the outlet ducts. A sill, which interrupts the circulating flows, is arranged in each of the annular ducts of the pump casing, between the outlet ducts and the inlet ducts. This peripheral pump is maintenance-free and has a high level of efficiency. The form of the blades in which they rise from the central region of the rotor toward its end sides reduces impact losses which are caused by the liquid striking the front side or flowing around the blades. These impact losses always occur when the liquid to be delivered passes from the annular ducts into the region of the rotor. Furthermore, this design of the blades accelerates the liquid, when it enters the annular ducts, to a velocity which initially, as seen in the direction of rotation of the rotor, is higher than the velocity of the blades. Then, the velocity decreases in the direction of rotation of the rotor, while the velocity transverse to the direction of rotation increases. Consequently, the circulating flows are in the form of a lance directed in the direction of rotation of the rotor, leading to a high delivery pressure of the peripheral pump.
A drawback of the known peripheral pump is that it has two inlet ducts and two outlet ducts. This desien leads to an unnecessarily high installation outlay on the peripheral pump. Furthermore, owing to its two delivery chambers which are separated from one another by the central web, the peripheral pump has a large structural volume.
Axial flow peripheral pumps having a single outlet duct and a single inlet duct have already been disclosed, in which pumps the liquid flows over from one delivery chamber to the other delivery chamber. In this case, the liquid flows through the rotor in a radially outer region of the blade chambers. However, this design leads to an unfavorable circulating flow profile which has to be diverted by guide elements on the rear sides of the blades. These guide elements are also intended to reduce the impact losses on the inlet side. However, these guide elements cause friction losses and take up a considerable portion of the volume of the delivery chambers. As a result, the peripheral pump has a lower delivery volume and a lower delivery pressure compared to other peripheral pumps.